diff --git a/devito/types/sparse.py b/devito/types/sparse.py
index 676efe2b61..85ae824a80 100644
--- a/devito/types/sparse.py
+++ b/devito/types/sparse.py
@@ -989,6 +989,8 @@ class SparseTimeFunction(AbstractSparseTimeFunction, SparseFunction):
 
     is_SparseTimeFunction = True
 
+    is_regular = False
+
     __rkwargs__ = tuple(filter_ordered(AbstractSparseTimeFunction.__rkwargs__ +
                                        SparseFunction.__rkwargs__))